In order for a hard-copy imaging support to be widely accepted by the consumer for imaging applications, it has to meet several requirements. Consumer preference for ‘imaging media’, as documented in ‘voice-of-customer’ surveys, typically constrains certain fundamental imaging support properties, such as basis weight, caliper, stiffness, smoothness, and gloss, within a narrow range. Supports with properties outside the typical range for ‘imaging media’ suffer low consumer acceptance.
In addition to these fundamental requirements, imaging supports are also subject to other specific requirements depending upon the mode of image transfer onto the support. For example, in the formation of photographic paper, it is important that the photographic paper be resistant to penetration by liquid processing chemicals failing which there is present a stain on the print border accompanied by a severe loss in image quality. In the formation of ‘photo-quality’ inkjet paper, it is important that the paper is readily wetted and that it exhibit the ability to absorb high concentrations of ink and dry quickly, failing which elements block together when stacked against subsequent prints and exhibit smudging and uneven print density. For thermal media, it is important that the support contains an insulative layer in order to maximize the transfer of dye from the donor that results in higher color saturation.
It is important therefore, for an imaging media, to simultaneously satisfy several requirements. One commonly used technique in the art for simultaneously satisfying multiple requirements is through the use of composite structures comprising multiple layers wherein each of the layers, either individually or synergistically, serve distinct functions. For example, it is known that a photographic paper comprises a cellulose paper base that has applied thereto a layer of polyolefin resin, typically polyethylene, on each side, which serves to provide waterproofing to the paper and also provides a smooth surface on which the photosensitive layers are formed. For example also, in U.S. Pat. No. 5,866,282, biaxially oriented polyolefin sheets are extrusion laminated to cellulose paper to create a support for silver halide imaging layers. The biaxially oriented sheets described therein have a microvoided layer in combination with coextruded layers that contain white pigments such as TiO2 above and below the microvoided layer. The composite imaging support structure described has been found to be more durable, sharper and brighter than prior art photographic paper imaging supports that use cast melt extruded polyethylene layers coated on cellulose paper. For example also, in U.S. Pat. No. 5,851,651, porous coatings comprising inorganic pigments and anionic, organic binders are blade coated to cellulose paper to create ‘photo-quality’ inkjet paper.
The composite imaging element, such as described above, is typically formed in long, wide sheets and then spooled into large rolls. These large wide rolls must then be converted into predetermined smaller sizes by slitting, chopping, and/or perforating the large wide rolls. It is important that the various conversion operations, also referred to as cutting processes, be performed without damaging the imaging element. It is also important that the conversion be performed without creating substantial amounts of dust or hair-like debris which might lead to undesirable contamination of imaging surfaces.
The generation of this hair-like debris is generally attributed to an adverse combination of stiffness and toughness of the various layers of the imaging element. A poor combination of stiffness and toughness properties of various layers results in uncontrolled crack propagation during cutting and the subsequent formation of hair-like debris. Poor layer material selection and/or layer ordering results in poor cutting performance. For example, there is a problem with the element described in U.S. Pat. No. 5,866,282 in that the cutting of this imaging element results in the creation of substantial amounts of hair-like debris which is highly undesirable. The poor cutting performance may be traced to the poor material selection and ordering in the composite, resulting in an adverse combination of stiffness and toughness of the various layers of the imaging element and uncontrolled crack propagation during cutting.
Polymer foams have previously found significant application in food and drink containers, packaging, furniture, appliances, etc. They are also referred to as cellular polymers, foamed plastic or expanded plastic. Polymer foams are multiple phase systems comprising a solid polymer matrix that is continuous and a gas phase. For example, U.S. Pat. No. 4,832,775 discloses a composite foam/film structure which comprises a polystyrene foam substrate, oriented polypropylene film applied to at least one major surface of the polystyrene foam substrate, and an acrylic adhesive component securing the polypropylene film to said major surface of the polystyrene foam substrate. The foregoing composite foam/film structure can be shaped by conventional processes as thermoforming to provide numerous types of useful articles including cups, bowls, and plates, as well as cartons and containers that exhibit excellent levels of puncture, flex-crack, grease and abrasion resistance, moisture barrier properties and resiliency. Foams have also found limited application in imaging media. For example, JP-2839905 B2 discloses a 3 layer structure comprising a foamed polyolefin layer on the image-receiving side, raw paper base and a polyethylene resin coat on the backside. Another variation is a 4 layer structure highlighted in JP-09106038 A. In this, the image receiving resin layer comprises of 2 layers, an unfoamed resin layer which is in contact with the emulsion, and a foamed resin layer which is adhered to the paper base.
U.S. patent application Ser. No. 09/723,518, filed Nov. 28, 2000, discloses an imaging element comprising an imaging layer and a base wherein said base comprises a closed cell foam core sheet and adhered thereto an upper and lower flange sheet, and wherein said imaging member has a stiffness of between 50 and 250 milliNewtons. Although this imaging element is suitable for imaging applications, an adverse material selection for each of the elemental layers can, during conversion, result in uncontrolled cracks which tend to branch into the core/flange interface and, subsequently, tear the flange layer at a location away from the moving knife thus, creating hair-like debris which hangs onto the cut edge. This debris may then fall onto the imaging surface during subsequent handling of the imaging element.